In the work are researched problems, which arise during hiding of messages in text environments, being transmitted by electronic communication channels and the Internet. The analysis of selection of places in text environment (TE), which can be replaced by word from the message is performed. Selection and replacement of words in the text environment is implemented basing on semantic analysis of text fragment, consisting of the inserted word, and its environment in TE. For implementation of such analysis is used concept of semantic parameters of words coordination and semantic value of separate word. Are used well-known methods of determination of values of these parameters. This allows moving from quality level to quantitative level analysis of text fragments semantics during their modification by word substitution. Invisibility of embedded messages is ensured by providing preset values of the semantic cooperation parameter deviations.